1. Field of the Invention
The present invention relates to an engine automatic stop-start controller having a function to determine existence/nonexistence of a misfire in a cylinder (first ignition cylinder) that performs ignition first in automatic start.
2. Description of Related Art
In a vehicle mounted with an engine automatic stop-start system (idle stop system), an automatic start condition is established and the engine is started automatically when a driver performs an operation for starting the vehicle (e.g., brake release) during automatic stop (idle stop). If a misfire occurs in a cylinder (first ignition cylinder) that performs ignition first in the automatic start, startability worsens and the driver feels that the start is slow. Moreover, problems such as exhaust emission deterioration occur.
Therefore, as described in Patent document 1 (Japanese Patent No. 4029474), there is a system that measures a start time and determines that the startability has deteriorated if the start time exceeds an abnormality determination threshold value. When the system determines that the startability has deteriorated, the system prohibits or restricts the automatic stop (idle stop).
However, the start time fluctuates due to many factors such as a state of a starting device, a charged state of a battery and an electric load. Therefore, it is required to set the abnormality determination threshold value of the start time at a relatively large value in consideration of the above many fluctuation factors in order to prevent erroneous determination of the abnormality. Therefore, it is difficult for the technology of Patent document 1 to determine whether the cylinder (first ignition cylinder) that performs the ignition first in the automatic start has caused a misfire.